Articulated assembly of two links, and associated removal chain

ABSTRACT

Disclosed is an articulated assembly of two links for a ballast removal chain, a first of the two links comprising a single-piece member having two flanges which are parallel to one another and each of which has a through-hole, a second of the two links comprising a single-piece member comprising a guide flange that is inserted between the two parallel flanges of the first link, the guide flange being penetrated by a guide hole, the articulated assembly further comprising a hinge pin that is inserted into the guide hole and the through-hole in each of the two parallel flanges. The guide hole is reinforced by a bushing designed to receive the hinge pin and rotatingly guide the hinge pin relative to the single-piece member of the second link. The through-hole in one of the two parallel flanges comprises a flat portion cooperating with a flat section of the hinge pin so as to prevent the hinge pin from rotating relative to the single-piece member of the first link.

TECHNICAL FIELD OF THE INVENTION

The invention relates, in a general manner, to the technical field ofclearance or excavation chains.

The invention relates more specifically to an articulated assembly oftwo links which are intended to equip an excavation chain for a devicefor clearing ballast under a railroad, to an excavation chain comprisinga link assembly of this kind, and to a method for manufacturing links ofthis kind.

PRIOR ART

In the prior art, work trains are known which are equipped with machinesintended for removing the ballast located under the sleepers of arailroad, and for sorting it for possible re-use by tipping into ontothe track. These machines are commonly referred to as “ballast clearingmachines.” In a known manner, work trains of this kind more generallycomprise a machine intended for screening the ballast in order on theone hand to keep the sound part of the ballast for re-use, and on theother hand to remove the spent part of the ballast, in trucks providedfor this purpose. In this way, the ballast clearing machine/cleanerattachment makes it possible to remove and sort the spent ballast, andreplace the entire ballast layer with the sorted sound ballast, as wellas optional additional supply of new ballast.

Work trains of this kind are equipped with excavation chains made up ofa succession of links which are articulated to one another, at leastsome of which are equipped with shovels intended for excavating theballast. Said chain is arranged on the chassis of the rail vehicle, soas to be movable or height-adjustable. The chain is driven in an endlessmanner by a drive mechanism. The path of the chain is configured suchthat it comprises a straight excavation portion located under thesleepers of the railroad, the chain working on this excavation portiontransversely with respect to the orientation of the rails of therailroad, carrying along and transporting the ballast with them. Oneither side of said straight excavation portion, brackets are arranged,which form return members for the excavation chain. Said brackets arelocated at the ends of the straight excavation portion, along whichportion the ballast is removed, and are generally formed by a bent fixedwall on which the links of the chain slide successively. The chain movesalong a longitudinal feed path and then moves over the straightexcavation portion after having passed through a first bent portionformed by one of the brackets. The chain which follows its path thenemerges from said straight excavation in order to move over thelongitudinal outlet portion after having passed through a second bentportion formed by the other of the brackets. The shovels arrive on saidstraight excavation portion having been unloaded, and re-emergetherefrom loaded with ballast, towards the longitudinal outlet portion.The longitudinal feed and outlet portions are connected, in a regionlocated at a height with respect to the rail vehicle, by a transversedischarge portion where the ballast is discharged onto conveyor belts.The shovels, offloaded of ballast, then continue their path towards thelongitudinal feed portion, then repeating these operations.

The document EP 2 848 735 A1 describes an example of shovels of theprior art.

Said shovels are designed to overcome a number of problems. Inparticular, they must be sufficiently resistant to ensure a certainnumber of predetermined cycles, in order to ensure the excavation andtransport of ballast, requiring minimum maintenance. Said shovels mustfurthermore allow for effective transport of the ballast towards thedischarge thereof, with a view to the screening operation, in order toimprove the output of the ballast clearing machine by the excavation ofthe ballast, as well as that of the cleaner attachment, in order to makeit possible to improve the reuse rate of the sound ballast.

In addition to these limitations, the excavation chain itself must besufficiently resistant for transporting said shovels, in order to ensurethe excavation and transport of ballast, requiring minimum maintenance.In particular, the assembly of links that are articulated together mustnot constitute a point of weakness for the chain, and must allow forsufficient pivoting in order to be able to pass the return members thatare arranged on the path thereof and are not stressed.

DISCLOSURE OF THE INVENTION

The invention aims to overcome all or some of the disadvantages of theprior art, by proposing in particular an articulation between two links,which is designed to limit the wear of said links, so as to be able toreduce the maintenance operations and guarantee a longer service life ofthe links and of the associated chain.

In order to achieve this, according to a first aspect of the inventionan articulated assembly of two links for an excavation chain for aballast excavation device is proposed, a first of the two linkscomprising a single-piece body having two flanges which are in parallelwith one another and with a reference plane of the articulated assembly,and through each of which a through-hole passes which is aligned with ageometric articulation axis of the articulated assembly, perpendicularto the reference plane, a second of the two links comprising asingle-piece body comprising a guide flange that is inserted between thetwo parallel flanges of the first of the two links, a guide hole passingthrough the guide flange, which guide hole is aligned with the geometricarticulation axis, the articulated assembly further comprising a hingepin that is inserted into the guide hole and the through-hole in each ofthe two parallel flanges, the articulated assembly being notable inthat:

-   -   the guide hole is reinforced by a bushing designed to receive        the hinge pin and to guide the hinge pin so as to rotate        relative to the single-piece body of the second link; and in        that    -   the through-hole of one or the other of the two parallel        flanges, referred to as the flange for preventing rotation of        the hinge pin, comprises a flat portion cooperating with a flat        region of the hinge pin so as to prevent the hinge pin from        rotating relative to the single-piece body of the first link.

Such a combination of features is particularly advantageous in that itmakes it possible to limit the wear of the hinge pin and the two linksof the assembly. Indeed, on the one hand the assembly is prevented fromrotating with respect to the first of the two links comprising the twomutually parallel flanges limiting the friction between said two parts,and on the other hand the assembly allows the rotation of the second ofthe two links in the region of the guide flange thereof, reinforced by abushing with the hinge pin of the assembly, forming a hinge.Furthermore, it allows for particularly simple mounting and dismantling.

The flat portion and the flat region are preferably located in a planein parallel with the geometric articulation axis. The very simple shapesresulting therefrom facilitate the formation of the hole comprising theflat portion, and make it possible in particular to envisage manufactureof the corresponding link by molding without reworking by machining.

According to an embodiment, one or other of the two flanges, in parallelwith the first of the two links, referred to as the flange forpreventing translation of the hinge pin, comprises a translationprevention interface which is designed to receive a means for preventingtranslation of the hinge pin in at least one direction in parallel withthe geometric articulation axis. The prevention means is preferablydetachable with respect to the prevention interface. In this way, themaintenance operation consisting in removing the hinge pin from theassembly between the two links is facilitated.

The translation prevention interface and the means for preventingtranslation of the hinge pin preferably do not prevent the rotation ofthe hinge pin about the geometric articulation axis.

According to an embodiment, the prevention interface is an annulargroove inside the through-hole associated with one of the two flanges ofthe first of the two links, the prevention means preferably comprisingan inner resilient ring. An annular groove of this kind is a relativelysimple shape to machine, and make it possible to receive the resilientring therein, such that the hinge pin is prevented from moving intranslation with respect to the geometric articulation axis.

More precisely, the hinge pin is prevented from moving in translationwith respect to the geometric articulation axis in a first direction, bybeing in abutment against said resilient stop ring, and being inabutment against a lateral surface of the flat portion.

According to an embodiment, the inner resilient ring has aquadrilateral, preferably rectangular, axial cross section, and morepreferably a square cross section. Such a cross section of the resilientring aims to increase its loading resistance.

According to an embodiment, the flange for preventing translation of thehinge pin is separate from the flange for preventing rotation of thehinge pin.

According to an embodiment, the first of the two links comprises aseparate second geometric articulation axis, which is perpendicular tothe reference plane. The flat portion of the through-hole is oriented soas to be contained in a plane. This plane is preferably perpendicular toa plane containing the two geometric articulation axes, and ispreferably located between the two geometric articulation axes. Such anorientation of the flat portion makes it possible to improve theprevention of rotation of the hinge pin in question, the force beingapplied to the flat region of the hinge pin.

According to an embodiment, the bodies of each of the two links is madeof cast steel, the flat portion of the through-hole of one of the twoflanges in parallel with the first of the two links being formedtogether with the body of the associated link, so as not to be machined.In this way, the single-piece body of the link can be manufactured veryeasily, and the flat portion is obtained at the same time.

According to an embodiment, the hinge pin comprises, on one of the twoends thereof, an anchoring interface, for example a threaded hole thatis coaxial with the geometric articulation axis, so as to allow it to begrasped by a tool in order to be manipulated. A feature of this kindfurther facilitates the maintenance of the assembly. The anchoringinterface is preferably a detachable fixing interface for ensuring thecooperation of the tool with the hinge pin, the time of just onemaintenance operation.

According to another aspect of the invention, this relates to anexcavation chain having an excavation portion for a device forexcavation of ballast under a railroad, the excavation chain beingnotable in that it comprises a succession of chain links which areconnected in pairs by an assembly as described above, so as to form anendless chain.

According to an embodiment, the excavation chain is formed by analternating succession of links forming the first link of an assemblywith each of the two adjacent links, and links forming a second link ofan assembly with its two adjacent links. Each link comprises a bodywhich extends longitudinally between a front end and a rear end. In thecase where the excavation chain is formed by such a successivealternation of links, each of the two ends of one first link forms afirst of the two links for an assembly with an adjacent second link, andeach of the two ends of one second link forms a second of the two linksfor an assembly with an adjacent first link.

Alternatively, one link has an interface like a first link at one of itsfront and rear ends, and forms an interface like a second link at theother of its front and rear ends.

According to another aspect, the invention also relates to a method formanufacturing a link intended to equip an excavation chain as describedabove, which is notable in that it comprises a step of molding,consisting in casting a metal or a liquid or pasty alloy, preferably ofsteel, into a mold.

According to an embodiment, the flat portion of the through-hole of oneof the two flanges in parallel with the first of the two links is formedtogether with the body of the associated link, during the molding step,so as not to be machined.

According to an embodiment, the manufacturing method comprises a step ofmachining, on one or other of the two flanges of the first of the twolinks, preferably separately from the flange for preventing rotation ofthe hinge pin, a rotation prevention interface for receiving a means forpreventing translation of the hinge pin, for example an annular grooveinside the associated through-hole.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the invention will become clear fromthe following description, given with reference to the accompanyingdrawings, in which:

FIG. 1 : is a simplified side view of a work train equipped with aballast clearing machine/cleaner attachment;

FIG. 2 : is a partial view of an excavation or clearing device, viewedfrom the front, without an excavation chain;

FIG. 3 : is a perspective view of an excavation chain portion accordingto an embodiment;

FIG. 4 : is a front view of an excavation chain portion according tothis embodiment;

FIG. 5 : is a cross section according to A-A in FIG. 4 ;

FIG. 6A: is an exploded view of a succession of links assembledaccording to this embodiment;

FIG. 6B: shows a detail of FIG. 6A, showing a perspective view of aresilient ring according to an embodiment;

FIG. 7 : is a plan view of a succession of assembled links intended forequipping an excavation chain;

FIG. 8 : is a partial view of the cross section B-B in FIG. 7 ;

FIG. 9 : is a partial view of the cross section C-C in FIG. 8 ;

FIG. 10 : is a side view of a first link according to an embodiment;

FIG. 11 : is a plan view of FIG. 10 ;

FIG. 12 : is a cross section according to D-D in FIG. 10 .

For reasons of improved clarity, the identical or similar elements areindicated by identical reference signs in all the figures.

DETAILED DESCRIPTION OF AN EMBODIMENT

With reference to FIG. 1 , a rail vehicle 1 such as a ballast clearingmachine/cleaner attachment equipped with a device for clearing orexcavation 4 for cleaning the ballast of a railroad track 2 is shown.Said clearing or excavation device 4 is arranged between two bogies 3 ofthe train 1.

The ballast clearing device 4 comprises an excavation chain 8 that isdriven in an endless manner by means of a drive mechanism 9, and guidedby pipes, including a transverse pipe 5 located under the track 2 in thework position, along which the chain circulates over a substantiallystraight excavation portion 8A. The clearing device 4 also comprisesriser pipes and downpipes 6, 7 which are connected on either side of thetransverse pipe 5 to which they are connected by bent portions formingangle returns 40, also referred to as “brackets” (see FIG. 2 ). It isunderstood that the excavation portion is generally straight, althoughthe excavation is ensured in a part of the curve of each of the anglereturns.

The drive device 9 is arranged at a height with respect to the railvehicle 1, above the railroad 2, on a side longitudinally opposite thetransverse pipe 5, and between the riser pipe 6 and the downpipe 7. Thedrive device 9 is positioned on the path of the excavation chain 8 andcomprises a drive wheel 9′ which engrains locally with the links 100 ofthe excavation chain 8 so as to move it. An endless path is thus formed,for guiding the excavation chain 8. Arrows shown in FIG. 2 indicate thedirection of movement of the chain 8. At the top ends of the riser pipe6 and downpipe 7, to the side of the drive device, idler wheels 41forming return members 40 are provided for ensuring expedient movementof the chain 8 in the region of these bent zones.

Once the ballast has been transported upwards in the riser pipe 6, it isdischarged onto a conveyor belt 10 and then transported to a screeningunit 11 with the aim of sorting the sound ballast from the spentballast.

The vehicle 1 further comprises a unit for lifting 13 the railroad 2,which is connected to a chassis 14 of the vehicle 1 and which is locatedupstream of the clearing or excavation device 4, with respect to a workdirection 12 of the vehicle 1. A height regulation device 16 is alsoprovided, and connected to the frame 14 of the vehicle 1, which isdesigned to move the clearing device 4, using drive means 15, from alifted position to a position lowered under the railroad 2, and whichcan be for example detachably connected to the transverse pipe 5 by aconnection (not shown in the drawings).

FIGS. 3 and 4 show a portion of an excavation chain 8 according to anembodiment. The excavation chain 8 is formed of a succession of links100 which are articulated in pairs, until the two ends of the chain 8are connected end-to-end to form a closed chain 8, of the endless chaintype.

Each of the links 100 are articulated in pairs, in the region of theirrespective ends. More precisely, each assembly of two articulated linksis formed between a first link 101 and a second link 102. Eacharticulation between two links is achieved by an assembly 10, thedetails of which are illustrated in particular in FIGS. 5 and 9 .

The first 101 of the two links comprises a single-piece body 101′comprising two flanges 110 a, 110 b which are in parallel with oneanother and with a reference plane P of the articulated assembly 10. Athrough-hole 111, aligned with a geometric articulation axis X of thearticulated assembly 10, perpendicular to the reference plane P, passesthrough each of the two flanges 110 a. 110 b. FIGS. 10, 11 and 12 areviews of a link comprising articulation means at least of itslongitudinal ends, of which each end of the link is equipped with twomutually parallel flanges 110 a, 110 b, i.e. the link is a first link,both with respect to the assembly 10 which connects it to the adjacentfront link, and also with respect to the assembly which connects it tothe adjacent rear link.

The second 102 of the two links comprises a single-piece body 102′comprising a, preferably single, guide flange 120 which is insertedbetween the two parallel flanges 110 a, 110 b of the first 101 of thetwo links, a guide hole 112 aligned with the geometric articulation axisX passing through the guide flange 120.

The articulated assembly 10 further comprises a hinge pin 160 that isinserted in the guide hole 112 and the through-hole 111 of each of thetwo parallel flanges 110 a, 110 b. In this manner, the hinge pin 160allows for the connection between the first and second links 101, 102 soas to form a hinge between these two links. The first 101 of the twolinks forms a female interface, with its two flanges 110 a, 110 b, inorder to receive, between the two, the guide flange 120 of the second102 of the two links 101, 102 forming a male interface which links andcouples, by means of the hinge pin 160, with the associated femaleinterface.

In order to limit the wear between the second link 102 and the hinge pin160, the guide hole 112 is reinforced by a bushing 113 which is designedfor receiving the hinge pin 160 and for guiding the hinge pin 160 inrotation with respect to the body 102′ of the second link 102. Thebushing 113 is preferably shrunk on, for example cold shrunk on, in theguide hole 112 of the body 102′ of the second link 102 made of manganesesteel. In this way, the bushing 113 is arranged so as to be coaxial tothe geometric articulation axis X and designed to be in a pivotconnection with the hinge pin 160, said bushing 113 being kept fixed inthe body 102′ of the second link, in particular in the guide hole 112.The bushing is housed integrally in the guide hole 112 of the guideflange 120, so as not to project, which makes it possible to limit thefriction between the parts of the assembly 10. In other words, thebushing 113 is preferably either flush, or slightly retracted withrespect to the laterally emerging ends of the guide flange 120, in theguide hole 112, in order to avoid a projection of this kind.

In order to further limit the wear of the articulation 10, between thefirst flat region 101 and the hinge pin 160 the through-hole 111 and one110 b of the two parallel flanges comprises a flat portion 105 whichcooperates with a flat region 161 of the hinge pin 160 in order toprevent rotation of the hinge pin 160 with respect to the single-piecebody 101′ of the first link 101 (see for example FIGS. 8 and 9 ). Sincethe rotation about the geometric articulation axis X is prevented, thefriction is limited. The pivot articulation between the first and secondlinks 101, 102 of the assembly 10 is, in turn, always allowed by thedegree of rotational freedom of the second link 102 with the hinge pin160.

A link 100 of the chain 8 comprises a front end and a rear end. In thismanner, the first link 101 of the assembly has a separate secondgeometric articulation axis, in parallel with the first andperpendicular to the reference plane P. The flat portion 105 of thethrough-hole 111 is oriented so as to be contained in a plane Pp that isperpendicular to a plane containing the two geometric articulation axesX and perpendicular to the reference plane P. An orientation of thiskind promotes absorption of forces, depending on the advancementdirection of the chain 8 and the direction of rotation of the links withrespect to one another when they pass certain obstacles such as thereturn members 40.

In order to retain the hinge pin in the articulated assembly, and inparticular to prevent its translational motion according to thegeometric articulation axis X, this is locked in both directions.Indeed, the hinge pin 160 comprises a substantially cylindrical body,one end of which is provided with a flat region 161. In a configurationof this kind, an intermediate part of the hinge pin 160 is cylindricalso as to ensure the pivot connection to the second link 102 in the guidehole 112 of the guide flange 120. The cylindrical part is separated fromthe flat region 161, according to the axis of the hinge pin 160, by anindentation 163 that extends in a plane perpendicular to the geometricarticulation axis X of the assembly 10.

In the assembled position, the indentation 163 of the hinge pin 160comes into contact with and bears against an inner face 110 b′ of theflange 110 b on a lateral edge 105′ of the flat portion 105, whichallows for locking of the hinge pin 160 in a first direction.

In order to ensure the prevention of the translation of the hinge pin160 in the opposite direction, one 110 a of the two flanges, in parallelwith the first 101 link comprises a translation prevention interface 103which is designed to receive a means 104 for preventing translation ofthe hinge pin 160. In particular, the prevention interface 103 is anannular groove which is machined, in this case bored, in the inside ofthe associated through-hole 111. The prevention means 104 comprises aninner resilient stop ring which comes to rest in the annular groove 103,and a portion of which is positioned on the path of the hinge pin 160 inorder to form an obstacle for it and to prevent its movement intranslation. In particular in order to allow for better retention of theresilient ring 104 in the bored groove 103, said resilient ring 104 hasa quadrilateral, preferably rectangular, cross section. In order toensure optimal locking of the hinge pin 160, every means for preventingthe hinge pin 160 from moving in translation in a given direction isborne by two separate flanges of two parallel flanges 110 a, 110 b, i.e.the flange 110 a of the first 101 of the two links comprising theannular groove 103 is separate from the flange 110 b of the first 101 ofthe two links comprising the flat portion 105.

A resilient stop ring 104 is illustrated in greater detail in FIG. 6B.The resilient ring 104 comprises a body 104 a extending in an annularmanner over a particular angular sector, preferably larger than 240°,defining an inner space 104 c. The body 104 a comprises, at each of theends thereof, ears 104 b which extend radially towards the inside 104 cof the body 104 a and are designed to be grasped by a tool such aspliers. The resilient ring 104 is formed as a single piece, i.e.integrally. The resilient ring 104 is formed of a solid material, i.e.which does not comprise any holes, whether on its body 104 a or its ears104 b. The resilient ring 104 is formed of steel for example.

The ears of the resilient ring 104 each comprise a bend 104 d such thatthe end part faces in the direction away from the other ear. This allowsfor stiffening and reinforcement of the load resistance.

The resilient ring 104 is designed to be inserted into and to cooperatein a groove 103 in order to lock the hinge pin 160 in a direction oftranslation according to the geometric articulation axis X. Theresilient ring 104 is dimensioned such that it is in contact with andbears, radially with respect to the geometric articulation axis X,against a bottom of the circular groove when it is positioned in saidgroove 103.

The hinge pin 160 comprises an anchoring interface 162 such as athreaded hole that is coaxial with the geometric articulation axis X, soas to allow it to be grasped by a tool in order to be manipulated. Saidanchoring interface 162 is located on the side of the assembly where theresilient ring 104 is mounted in one 110 a of the two parallel flangesof the first link 101, i.e. on the side the operator must access inorder to perform the mounting and dismantling of the assembly 10. In theregion of the hinge pin 160, the anchoring interface 162 is located atone of the ends thereof, opposite that comprising the flat region 161.In order to carry out the maintenance of each assembly 10, the operatormay act from the same side of the chain 8, using pliers in order toremove the resilient ring on the one hand, and using a suitable tool,for example a slide hammer, for cooperating with the threaded hole 162leading onto a face of the end of the hinge pin 160 on the other hand.

Each of the links 100, 101, 102 comprises a body 101′, 102′ whichextends longitudinally between a front end and a rear end. In this case,the longitudinal direction extends as the direction of movement of thelink 100. Each link 100, 101, 102 is connected, in a manner articulatedto two other adjacent links of the chain 8, to each of the front andrear ends thereof. Each link is articulated, at the two front and rearends thereof, with an adjacent link, such that one link is articulatedby two separate assemblies 10, longitudinally on either side of itsbody.

Each articulation between two links is formed by an assembly 10, asdescribed in detail above. It follows that each end of the link isdesigned, in this case, either as a first 101 of the two links of theassembly in question, or as a second 102 of the two links of theassembly in question. In particular, in this case:

-   -   a first group of links of the chain 8 comprises, for each of the        links, on one side, a first end forming a first link 101 of an        assembly, and, on another side, a second end, opposite the        first, which also forms a first link 101 of another assembly:        and    -   a second group of links of the chain 8 comprises, for each of        the links, on one side, a first end forming a second link 102 of        an assembly, and, on another side, a second end, opposite the        first, which also forms a second link 102 of another assembly.

Preferably, each link body 101′, 102′ is symmetrical with respect to aplane of symmetry perpendicular to the longitudinal axis thereof andperpendicular to the reference plane P, but also perpendicular to aplane containing the two geometric articulation axes X. In other words,and for each of the links of the chain 8, the front end is substantiallysymmetrical with respect to the rear end.

As already mentioned, the first 101 of the two links of a given assemblyforms an interface referred to as “female,” with its two flanges 110 a,110 b, in order to receive, between the two, the guide flange 120 of thesecond 102 of the two links 101, 102 forming an interface referred to as“male” which links and couples, by virtue of the hinge pin 160, with theassociated female interface. Thus, in the embodiment as shown, each linkbody comprises one similar interface, female or male, at the two endsthereof, hence the simplified term of “link” which can be used to referto it in the chain 8, either a female chain link or a male chain link.

Of course, the arrangement of the assemblies in the chain 8 may bedifferent. For example, one link may comprise, on one side, a first endforming a first link 101 of a first assembly, and, on another side, asecond end, opposite the first, forming a second link 102 of anotherassembly.

As shown in particular in FIGS. 3, 4, 6A and 7 , the excavation chain 8is made up of a succession of links 100, among which the links are ofthree different types, although they each comprise a body designedeither as a male link 102 or as a female link 101.

The excavation chain comprises the links 100 of the type comprising ashovel 130, the links 100 of the type comprising a counter stop 140, andthe links 100 of the type without a projecting part, i.e. formedessentially on their body 101.

The function of such links 100 without a projecting part is primarilythat of making the excavation chain 8 more lightweight. Another functionis that of better adjusting the volume of excavated ballast to themaximum capacity of the screen, without losing too much of its owncapacity, which is reduced by an order of magnitude of 20%, and not 50%as a person skilled in the art may think on account of the substantiallydoubled space between two shovels 130 in a design of this kind. This ismade possible in particular by virtue of the shovel 130 which is similarto that described above, and in particular the tilting thereof.

In this embodiment, each of the links 100 of the type comprising ashovel 130 is arranged between two links 100 of the type comprising acounter stop 140. Furthermore, each link 100 without a projecting partis also arranged between two links of the type comprising a counter stop140. One link in two is thus provided with a counter stop 140, the otherlinks alternately being a link of the type comprising a shovel 130 and alink of the type without a projecting part.

A pattern of the chain 8 is thus formed by a link 100 of the typewithout a projecting part, interposed between two links of the typecomprising a counter stop 140, and a link 100 of the type comprising ashovel 130 at a front or rear end of said set of three links: these fourlinks 100, together and in this order, form a pattern which is repeatedsuccessively along the chain 8.

According to the examples shown, the links 100 of the type comprising ashovel 130 and of the type without a projecting part are female links,and the links 100 of the type comprising a counter stop 140 are malelinks.

A configuration of this kind has several advantages. Said link 100comprising a shovel 130 comes directly in front of a link comprising acounter stop 140 in such a way, as already described, as to limit arelative rotation of the link bearing the shovel 130. Furthermore, aconfiguration of this kind makes it possible, on the one hand, to ensurea sufficiently small space between the links comprising a shovel 130 toensure the effective excavation and transport of the ballast, and, onthe other hand, to ensure a sufficiently large space to ensure theexpedient movement of the chain with the necessary flexibility forpassing the return members 40.

In order to ensure effective and lasting protection of the articulationsof the links 100 of the chain 8 against wear due to abrasion by theballast, and against the action of dust, thus conferring a longerservice life of the links 100 of the chain 8, the front and rear ends ofthe bodies 101′, 102′ of the links 100, 101, 102 each comprise a convexcurved portion, for example a longitudinal end that is rounded in acircular arc shape, such that it does not have sharp edges. Each curvedportion preferably extends over a casing having a generatrix in parallelwith the associated geometric articulation axis X. Said convex curvedportions forming rounded ends are carried by each of the parallel 110 a,110 b and guide 120 flanges. Furthermore, for the same assembly, theconvex curved portions of each of the parallel 110 a, 110 b and guide112 flanges through which the same hinge pin 160 passes have asubstantially identical radius of curvature, such that, when thearticulation passes a return member, the contact of the articulation onthe return member is distributed over the first and second links 101,102 that are articulated together.

In order to further reduce the risk of premature wear of the assembly,and thus of the articulation, the guide flange 120 exhibits clearancewith respect to the two other parallel flanges 110 a, 110 b, betweenwhich it is positioned, which is sufficient for preventing frictionduring their relative rotation, but is sufficiently small to avoidallowing the ballast to become lodged in the articulation.

Along the straight portion of the excavation 8A, the links 100 movetransversely with respect to the railroad 2, which corresponds to thelongitudinal direction of the bodies 101 of the links 100 on saidportion. The links 100 are oriented such that the geometric axes X ofeach of the articulations 10 are substantially vertical with respect tothe ground, the reference plane P thus being horizontal, and the shovel130 or the counter stop 140 extending substantially radially towards theoutside of the body of the associated link 100. The outer side of thelinks corresponds to the side where the ballast is excavated andtransported. An internal side of the bodies 101′, 102′ of the links isin turn designed to come into contact with and to come to bear againstthe return members 40 on the path traveled by the chain 8. Given thevertical orientation of the geometric axes X, it is possible tounderstand the interest in the hinge pins 160 being located entirely inthe space delimited by the through-holes 111 and the guide holes 112, soas not to project vertically, below or above, from the bodies of thelinks. Indeed, a design of this kind prevents wear of the hinge pins 160of each assembly 10.

In this embodiment, the links 100 are produced for example frommanganese steel and are formed integrally. An example of the method formanufacturing said link 100, obtained by smelting, comprises at leastone step of metal injection, and in particular a step of molding in amold formed for example of a form and an associated counter-form.

The bodies 101′, 102′ of each of the links 100, 101, 102 is made of caststeel, the flat portion 105 of the through-hole 111 of one 110 b of thetwo flanges in parallel with the first 101 of the two links being formedtogether with the body 101′ of the associated link, so as not to bemachined. In this manner, the only machining required on the bodies ofthe links 100 participating in the assembly relates to the bore 103designed for receiving the resilient ring 104.

Of course, the invention is described above by way of example. It willbe understood that a person skilled in the art is able to implementdifferent variants of the invention, without in any way departing fromthe scope of the invention.

1. An articulated assembly of two links for an excavation chain of aballast excavation device comprising: a first of the two linkscomprising: a single-piece body having two flanges which are in parallelwith one another and with a reference plane of the articulated assembly,and through each of which a through-hole passes which is aligned with ageometric articulation axis of the articulated assembly, perpendicularto the reference plane, and the second of the two links comprising: asingle-piece body comprising a guide flange that is inserted between thetwo parallel flanges of the first of the two links, a guide hole passingthrough the guide flange, which guide hole is aligned with the geometricarticulation axis, the articulated assembly further comprising a hingepin that is inserted into the guide hole and the through-hole in each ofthe two parallel flanges wherein the guide hole of the articulatedassembly is reinforced by a bushing designed to receive the hinge pinand to guide the hinge pin so as to rotate relative to the single-piecebody of the second link; and the through-hole of one or the other of thetwo parallel flanges, referred to as the flange for preventing therotation of the hinge pin, comprises a flat portion cooperating with aflat region of the hinge pin so as to prevent the hinge pin fromrotating relative to the single-piece body of the first link.
 2. Thearticulated assembly of claim 1, wherein the flat portion and the flatregion are located in a plane in parallel with the geometricarticulation axis.
 3. The articulated assembly of claim 1, wherein theone or other of the two flanges, in parallel with the first of the twolinks, referred to as the flange for preventing translation of the hingepin, comprises a translation prevention interface which is designed toreceive a means for preventing translation of the hinge pin in at leastone direction in parallel with the geometric articulation axis.
 4. Thearticulated assembly of claim 3, wherein the translation preventioninterface and the means for preventing translation of the hinge pin donot prevent the rotation of the hinge pin about the geometricarticulation axis.
 5. The articulated assembly of claim 4, wherein thetranslation prevention interface is an annular groove inside the holethrough the flange for preventing translation of the hinge pin.
 6. Thearticulated assembly of claim 5, wherein the means for preventingtranslation comprises an inner resilient ring that has quadrilateral,axial cross section.
 7. The articulated assembly of claim 3, wherein theflange for preventing translation of the hinge pin is separate from theflange for preventing rotation of the hinge pin.
 8. The articulatedassembly of claim 1, wherein the first of the two links has a separatesecond geometric articulation axis, perpendicular to the referenceplane, the flat portion of the through-hole being oriented so as to becontained in a plane that is located between the geometric articulationaxis of the articulated assembly and the separate second geometricarticulation axis, perpendicular to a plane containing the two geometricarticulation axes.
 9. The articulated assembly of claim 1, wherein thebody of each of the two links is made of cast steel, the flat portion ofthe through-hole of one of the two flanges in parallel with the first ofthe two links being formed together with the body of the associatedlink, so as not to be machined.
 10. The articulated assembly of claim 1,wherein the hinge pin comprises, on one of the two ends thereof, ananchoring interface, to allow it to be grasped by a tool in order to bemanipulated.
 11. An excavation chain having an excavation portion for adevice for excavation of ballast under a railroad, the excavation chaincomprising a succession of chain links which are connected in pairs byan assembly, so as to form an endless chain.
 12. The excavation chain ofclaim 11, wherein the chain is formed by an alternating succession oflinks forming the first link of an assembly with each of the twoadjacent links, and links forming a second link of an assembly with itstwo adjacent links. 13-15. (canceled)
 16. The articulated assembly ofclaim 10, wherein the anchoring interface is a threaded hole that iscoaxial with the geometric articulation axis.
 17. (canceled)